Typically, a fabric or textile is a flexible woven material consisting of a network of artificial fibers. Fabrics have an assortment of uses, the most common of which are for clothing and containers such as bags and baskets. In the household, fabrics are used in window blinds, carpeting, upholstered furnishings, towels, covering for tables, beds, and other flat surface.
Often, in preparing window blinds, the edges of a thermoplastic fabric along the longitudinal side edge portions must have an aesthetically pleasing appearance without unraveling of the fibers at the edges. Also, if continuous lengths of the fabric are cut transversely and parallel, the cut edges must have the same characteristics.
In many cases, for any type of fabric cutting method, the straight cut edge may not coincide exactly with a cutting line. All fabrics have natural variations as the individual fibers flex and they are not intended to align exactly with the edges. Consequently, as the fabric is cut, the fibers that orient perpendicular to the cut get cross cut cleanly, exposing the butt ends of the threads. However, the fibers that run parallel to the direction of the cut get ripped lengthwise through the thread, creating a frayed edge.
This problem often occurs with a straight knife type blade or rotary knife. A crush style cut that sheers the fabric by pinching it between two plates also results in frayed edges due to the ripped parallel fibers. In some instances, a certain method uses heat to cut the fabric, thereby solving one problem by marginally sealing the butt ends of the cross cut threads to prevent them from unraveling. However, the threads that are ripped lengthwise are still loose and will fray.
In yet another method, heat sealing the edge of the fabric after it is cut takes the edge of the fabric and presses and heats it to seal the edge. This heat sealing method melts and seals the edge with heat from a radio frequency or impulse sealers. This results in a seal that helps prevent both the cross cut and ripped threads and prevents fraying. However, because the fabric has already been cut, it is difficult to seal the very edge unless it is done with a wide seal, such as ¼″ to ½″. Those skilled in the art recognize that any seal narrower than ¼″ cannot be done reliably because of the stretch and tolerances of the fabric.
For example, a 1/16″ seal is not practical because the edge of the fabric wavers by more than 1/16″. In many cases, the edge of the fabric for window blinds will be 8 feet long or more. This wide seal along the edge produces a dark band down each side of the shade and is not aesthetically pleasing.
Even though the above cited methods for cutting and sealing a fabric address some of the needs of the market, a method and apparatus for cutting and sealing a fabric to form at least one fused edge, including a left and right edge of a shade fabric is still desired.